Patent GB-811579-A (GB)
Title: Improvements relating to photographic processes
IPC: G03C8/06
Filed: 1955-10-17
Abstract: 811,579. Photographic processes. INTERNATIONAL POLAROID CORPORATION. Oct. 17, 1955 [March 29, 1955; April 1, 1955(2)], No. 29519/55. Class 98(2) A fluid composition is spread between two superposed layers, at least one of which is transparent, the layers and the composition, in some cases with the aid of an intermediate layer, containing between them all that is necessary to provide or prepare a photosensitive heavy metal salt and processing materials therefor, photo-exposure is effected before extensive fogging occurs and an image is allowed to develop, usually with formation of a transfer-reversal image. When the reversal image, a positive, is considerably more dense than the negative image resulting directly from the exposure the two layers need not be separated, but preferably separation is effected to reveal the positive in one of the originally superposed layers or in a layer formed from the fluid composition. The invention is described with reference to sixteen figures for the layer assembly using silver halide as sensitive material, but it is stated that a photo-sensitive ferric diazonium or bichromate salt are available for the formation of a colour print where these materials display a suitable colour sensitivity. In Fig. 1, support 10 carries gelatino silver halide stratum 12, support 14 carries silverreceptive tratum 16, and container 18 therebetween carries an alkaline aqueous solution 20 of a silver halide developer and a silver halide solvent, and the process is effected by spreading the solution between the layers as by advancing the unit be- I tween a pair of pressure-applying rollers, exposing the silver salide stratum 12 after one second or less through the lens of a camera. Development and image transfer take place and stratum 12 together with the layer of solution are stripped off to reveal the positive print in layer 16. In a modification of the unit of Fig. 1 the developed includes a film forming material and silver precipitating nuclei and the posite print is formed in the dry residue of such. Numerous materials for construction of the unit and preparation of the developer solution are described. In Fig. 4, sheet 122 overlies sheet 120 coated with a stratum 126 in which are dispersed an alkali, a silver halide solvent and a silver precipitating agent, and the container 124 carries an aqueous composition containing silver halide and a developer therefor in inactive non-alkaline condition; pressure on this unit produces the photosensitive stratum which is exposed and allowed to develop in the manner of the unit of Fig. 1. The unit of Fig. 11 is designed for long storage and has a container 190 divided into compartment 192 as for silver nitrate and compartment 194 for a salt having halide ions so that silver halide may be formed only by action of compressional forces on the container. Figs. 12 and 13 (not shown) are somewhat similar, having separate containers arranged for effecting a time delay in production of the siver halide, and for adding already formed silver halide to alkaline developer before spreading the mixture respectively. Fig. 14 employs a lenticular screen member 317 and Fig. 16 an additive colour screen 325 for use with panchromatic sensitive materials to result in colour pictures. Figs. 5, 6 (not shown) illustrate a camera in which the silver halide layers may be exposed. Specifications 684,592, 684,599, 703,231, 714,412, 730,722, 776,634, 784,076 and 804,972 are referred to.